records: exposing record metadata revisions

(addresses #1990)

* Extends `get_record` with optional `revision` parameter
* Exposes revision for record information (metadata) tab
* Adds a config variable CFG_RECORD_REVISION_URL_PARAMETER
  with default value of "revision"

Signed-off-by: Bogdan Kulynych <bogdan.kulynych@gmail.com>
1: D400 First line should end with '.', not 'o'
1: D200 One-line docstring should not occupy 2 lines
2: I102 copyright year is outdated, expected 2014 but got 2011
21:1: E302 expected 2 blank lines, found 1
21: D202 No blank lines allowed *after* function docstring, found 1
21: D205 Blank line missing between one-line summary and description
21: D300 Expected """-quotes, got '''-quotes
35:14: E222 multiple spaces after operator