fix a confusing convention where line number are 1 based while column numbers are 0 based.

This commit change the convention so that all numbers are 0 based (it makes more sense and will make integration with other app easier and more coherent).

All tests are now passing locally but I have yet to update comments and fix status bar infos in examples to show both line number and column number as 1 based (0 based for programming, 1 based for display makes sense)
Fix the last test that was failing on travis
Fix goto dialog (dialogs and wigets are untested)
Fix clean document
Merged 'develop'.
Example: fix display of cursor position (display is 1 based)
Fix comments/doc
Fix test_code_edit

the entire module has been erased by a wrong manipulation

Also fix coverage rc (designer_plugin now has a leading _)
Merge pull request #145 from pyQode/feature/fix_confusing_convention

Fix confusing convention (line numbers are now 0 based)