Add export functionality

Exports Excel-REST modules/classes from specified workbook to specified
folder

Example:
(From Excel-REST folder)
`cscript build\export.vbs Workbook.xlsm src\`
Add import script

Imports Excel-REST into the library workbooks or the specified workbook

Example:
(From Excel-REST folder)
`cscript build\import.vbs`
`cscript build\import.vbs Workbook.xlsm`
Update build common helpers and simplify
Resolve build helper errors
Update build script helpers
Merge pull request #7 from timhall/build

Add import/export scripts