[log] Disable loading more details for filtering

* It looks like Git is able to filter faster on its own,
  than return us details.
* It is one step less, therefore if there are not many details,
  user will wait less time.
* It consumes less memory, since we don't expand the cache by extra n
  commits.

The code which handles "load more" is kept in the VcsLogDataHolder by
now: maybe this decision will be changed or somehow modified.
[log] Disable highlighting of current branch commits via background

Seems to be too aggressive right now, and better solution was not
found yet.

Making nodes & edges thicker is kept, so current branch is indicated
anyway.
[log] Better progress indicator text
[log] Remove temp icons, use some existing ones

Until new icons are ready, use collapseAll/expandAll icons.