Zhang Jing: Update pulling and merging capability
1. add a method in shellrunner.py for the "sdb pull" codes, and give related error message when the file is not available on device. then only 1 statement in main py for invoking.
2. remove useless attributes from <capabilities>
Merge remote-tracking branch 'upstream/master'

Conflicts:
	tct-shell
	tctshell/constants.py
	tctshell/shellrunner.py
Zhang Jing: Copy tmp/result.xml to the result folder
Zhang Jing: handle the case that running mode is None
Merge pull request #6 from iamrainius/master

Update for TCT-198 & TCT-200