Replaces always disabled context selection link

In the context selection dropdown, there is currently an always disabled
link to do more advanced filtering. The original intent was to open a
modal to do more advanced context selection. With the use of RBAC in a
previous bp, the Identity->Projects panel is always accessible. This
panel provides the entire project list for the user. We can just use
this to provide the larger project list to select from.

Change-Id: I0d6674e75785206f3be48c8bf004a29906bb6860
Closes-Bug: #1382650
Handle negative values in total*Used for Cinder absolute limits

In some cases negative values can be returned for resources currently
in use. When this occurs, the project overview page fails with an
error 500 due to an OverflowError, "cannot convert float infinity to
integer". Handle this case more gracefully.

Change-Id: Id1ad16eafdde906dc74bfafc7f72ea8d3bdcdc8f
Closes-Bug: #1386687
Missing a closing semicolon in _configure_general_help.html

This fix adds missing semicolon in _configure_general_help.html file
for &quot entity.

Change-Id: I04e0a806c6ed2d69be099992c7785129cced8829
Closes-Bug: 1386604
Clarify meaning of "Disk GB Hours" column

Admin > Overview Usage table has a column called "Disk GB Hours".
The meaning of this column is unclear.

Co-Authored-By: Thiago Paiva <thiagop@lsd.ufcg.edu.br>

Change-Id: I17e4a3ce60c66804e98a18c33261881ea10964b8
Closes-Bug: #1267362
Guard against `None` value of User.email attribute

If email was not specified during User creation (it's not required),
it will be `None`. It would be safer to guard against already existing
`None` values than to prevent creating new user with email == `None`.

Change-Id: Id81a94491918190ceae4b08cd3293250bb4ab194
Closes-Bug: #1383630
Merge "Handle negative values in total*Used for Cinder absolute limits"
Merge "Clarify meaning of "Disk GB Hours" column"
Merge "Missing a closing semicolon in _configure_general_help.html"
Merge "Guard against `None` value of User.email attribute"
Merge "Replaces always disabled context selection link"