Add [Index] link to package front page

If there is documentation for a package, display an "[Index]" link below
the list of modules, linking directly to the documentation index.

This is similar to #196, except the link is placed in the page body (as
per @dcoutts) rather than the header.

Closes #187.
fix typo
fix typo
unify the differences (currently duplicated code, but that's the next commit
extract out as top level function
use extracted function to get rid of duplication
Clean up test suite problems

1. Fix HTML5 validation warnings (by replacing <tt> with <code>).
2. Update user JSON response processing (to match
   a16d386c3c171de5a787a403039f284f4177f75e).
3. Update user deletion status code processing to recognise 204 "No
   content" response (to match af329c1241cc555696c46b2c120ecfaa33f24230).
make the email check for password recovery case-insensitive (fixes haskell/hackage-server#213))
Bump Cabal dependency to 1.20

This also adds more licenses (including BSD2 and AGPL and MPL) to the
tag generator.

Fixes #182.
Merge pull request #216 from lfairy/cabal-1.20

Bump Cabal dependency to 1.20
Merge pull request #209 from lfairy/doc-index-link

Add [Index] link to package front page
Merge pull request #212 from ian-ross/test-suite-fixups

Clean up test suite problems
Merge pull request #211 from fffej/master

Account creation fails with underscores in user names
Merge pull request #214 from alpmestan/case-insensitive-password-recovery

make the email check for password recovery case-insensitive (fixes haske...
use Data.Text.toCaseFold instead of toLower when comparing emails during password recovery. this closes haskell/hackage-server#214 for good
Merge pull request #217 from alpmestan/case-insensitive-password-recovery

use Data.Text.toCaseFold instead of toLower when comparing emails during...