add progress indicators

[Mark Mikofski]

for some transitions a progress dialog might be nice. eg loading issues

[Mark Mikofski]

this will require either a thread handler or asynchronous task, so it is not trivial.

[Mark Mikofski]

• add at startup to projects page in commit 9190c65579a9 and to details (milestones, issues, etc.) from projects
• add to issues page from prev, next, goto page number or filter/settings dialog box in commit c7ac5711498e
• still need progress bar for search, open new ticket #32