Check for unknown packages where catkin packages are required

The warning "not a catkin package" is slightly misleading if the
package in question does not exist at all.

Fixes #13
Preliminary support for column numbers

Eventually, this will allow checks for proper indentation.
Fix cache corruption with relative paths
Add cache dump option for debugging purposes
1.3.8
Merge version 1.3.8
1.3.8-1