WIP: Feature : Added dialog for batch export conflicts

Created a separate dialog for batch export which will handle files overwrite conflicts. Added options overwrite, skip files, add suffix (automatically).

Handle suffix and extension. Currently suffix is added after extension.

Currently for each file closest suffix is added. That is, if we export two objects rect31 and rect32 then, rect31_0.png (rect31.png exists) and rect32_1.png (rect31.png ad rect31_0.png exists) will be formed. This can be changed to common suffix to all conflicting files (more iterations) and common suffix for all files (even more iterations) after discussing with ux team.

Issues related: #2069 (closed)