added branch list view

This required making paged table module return an object per usage.
Also up'd commit list limit to 1500 and removed text show this limit
from statusbar.
Fixes #25 #23
update keys help overlay
fix paged table headers
show SHA for each branch in list
basic top-level tree from commit view working
basic working version of treeview

displaying blobs (aka files) in a tree not yet supported.
improve keybd help overlay
display all blobs contents in CM

for now even binaries get displayed and we dont set any specific
CM modes based on file types.
report progress reading repo to show commit log

Fixes #17