Update commands.py

updates fix that will cause an error if empty file

https://github.com/botherder/viper/issues/50
Merge pull request #51 from deralexxx/fix_empty_file_import

Update commands.py
Added possibility to switch between projects
Made help message more explicit
get_sample_count in database class
use new function to speed up startup
Merge pull request #54 from deralexxx/speed_up_count

Speed up count
Small fix
Small Fix to Dump option
Merge pull request #55 from kevthehermit/html

Small Fix to Dump option
Changed item to dash
Bumped release
Changed message for projects list
Started populating documentation
Replaced tabs with spaces
Introduced possibility to add multiple notes to the opened file
Added search by note, but not working yet
Fixed help messages
Added commands documentation
Added tags --delete command