Add errors if a project does not exist or contains errors in Settings.xml

[TaperChipmunk32]

• Check that the folder exists - else exit with the expected path shown in the error message.
• Check that the folder contains Settings.xml file - else exit with the expected path shown in the error message.
• Parse the Settings.xml file and ensure that at least one SFM file can be found using the naming convention specified. Else exit with a detailed error message. The error message can look for common sfm files by extensions (case insensitive) 'SFM', 'USFM', 'PT8' 'adescribe the apparent naming system of SFM files and how the Settings.xml file should specify them.