Prettify message view in held messages

This replaces and is inspired by the work done by @maxking in !9 

The added benefits of this merge request:
* use only one modal (no transitions when displaying full message)
* it also drastically decreases the website's size since it is only using one modal for all messages, relying on javascript to display the correct information

See merge request !52

Fix message when search returns no members

Display the appropriate message when no members are found in a search
on the members page.

Fixes #88

See merge request !89

Allow adding display name while mass subscribing

This patch will allow the mass subscribe form to accept
the display names for the addresses being subscribed.

fixes #63 

See merge request !127

Allow the mass subscribe form to accept
the display names for the addresses being subscribed.

Also change functionality so the "Please Choose" entry is only added
where it is actually needed, so that the number of available domains
actually matches the length of the returned list

Display the appropriate message when no members are found in a search on the members page.
Add the corresponding tests for the same.

Use ajax to display the message
Inspired by the work done by @maxking

Fix the KeyError encountered in mass removal method

Fix the KeyError encountered when performing mass-removal.

fixes #124 

See merge request !131

Fix indentation and line length

This limits the line length to 80 chars and fixes indentation errors

See merge request !111

Fix imports

This removes unused imports

See merge request !114

Remove unused variables

This removes unused variables

See merge request !115