Add Liberapay button in the donate section

* Update comment in database example config [#7282](https://github.com/diaspora/diaspora/pull/7282)

## Features

* Add support for [Liberapay](https://liberapay.com) donations [#7290](https://github.com/diaspora/diaspora/pull/7290)

# 0.6.3.0

<svg xmlns="http://www.w3.org/2000/svg" width="83" height="30">

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  <svg viewBox="0 0 80 80" height="16" width="16" x="7" y="7">

    <g transform="translate(-78.37-208.06)" fill="#1a171b">

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    </g>

  </svg>

  <text fill="#1a171b" text-anchor="middle" font-family="Helvetica Neue,Helvetica,Arial,sans-serif" font-weight="700" font-size="14" x="50" y="20">Donate</text>

</svg>

    AppConfig.settings.source_url.presence || "#{root_path.chomp('/')}/source.tar.gz"

  end

  def donations_enabled?

    AppConfig.settings.paypal_donations.enable? ||

    AppConfig.settings.liberapay_username.present? ||

    AppConfig.bitcoin_donation_address.present?

  end

  def timeago(time, options={})

    timeago_tag(time, options.merge(:class => 'timeago', :title => time.iso8601, :force => true)) if time

  end

- if AppConfig.settings.paypal_donations.enable?

  %p

    PayPal:

    %br

    %form{action: "https://www.paypal.com/cgi-bin/webscr", method: "post", target: "_blank"}

      %input{name: "cmd", type: "hidden", value: "_s-xclick"}

      - if AppConfig.settings.paypal_donations.paypal_hosted_button_id.present?

      %input{name: "hosted_button_id", type: "hidden", value: AppConfig.settings.paypal_donations.paypal_hosted_button_id}

        %input{name: "hosted_button_id", type: "hidden",

          value: AppConfig.settings.paypal_donations.paypal_hosted_button_id}

      - if AppConfig.settings.paypal_donations.paypal_unhosted_button_encrypted.present?

      %input{name: "encrypted", type: "hidden", value: AppConfig.settings.paypal_donations.paypal_unhosted_button_encrypted}

        %input{name: "encrypted", type: "hidden",

          value: AppConfig.settings.paypal_donations.paypal_unhosted_button_encrypted}

      %input{name: "currency_code", type: "hidden", value: AppConfig.settings.paypal_donations.currency}

    %input{name: "submit", type: "submit", value: t("aspects.index.donate"), class: "btn btn-default"}

      %input.btn.btn-default{name: "submit", type: "submit", value: t("aspects.index.donate")}

- if AppConfig.settings.liberapay_username.present?

  %p

    Liberapay:

    %br

    %a{id: "liberapay-button", href: "https://liberapay.com/#{AppConfig.settings.liberapay_username}/donate"}

      = image_tag "buttons/liberapay-button.svg",

          alt: t("aspects.index.donate"),

          title: t("aspects.index.donate_liberapay")

- if AppConfig.bitcoin_donation_address

  %p

    Bitcoin:

    %br

    %input{type: "text", id: "bitcoin_address", value: AppConfig.bitcoin_donation_address, readonly: true}

          .content

            != t("bookmarklet.explanation", link: link_to(t("bookmarklet.post_something"), bookmarklet_code))

        - if AppConfig.settings.paypal_donations.enable? || AppConfig.bitcoin_donation_address

        - if donations_enabled?

          .section.collapsed

            .title

              %h5.title-header