Implemented the use of colorChoices in ExportOptionsDialog.

Constructor input argument is a list that can contain the following strings: 'int', 'float', 'hex'. This determines what color options will be availble to the user. If colorChoices is empty, color options will not appear in the dialog. A new private attribute _colorChoices was added to keep track of color options between functions.
checkBoxList is also now private _checkBoxList
Added export options dialog to appear before exporting to a file.

Export options appear in OnFileExportFile of the MainMenu class. Each format has a different set of color and other options, which can be changed by changing colorChoices and otherChoices in OnFileExportFile.

Each format type in the formats folder has been changed to support different export options. The option argument in write() is now used and contains two keys, which are set in OnFileExportFile :
- colorOption is the index of the chosen color format
- checkedOptions is a list of the indices of the checked export options in the dialog