Just a round of fixes, I wanna try to add some of the feature recommended in #35 and #38, but I didn't get round to those this time round.

• Template generator: ID field allows duplicated special characters #30 Fixed the regex matcher to match all instead of only some
• Keep the main class names as the mod names in Template Mod Generator #26 Added -x (execute) unix permission for the gradlew file. This did require us to move over to using JSZip in platform: 'UNIX' mode, but I can't see any relevant downsides from this change.
• Template generator: ID field allows having no ID at all #31 / Template generator: ID field does not validate the min/max length #32 Moved some code around to support validation rules on both modId inputs to improve basic error checking on the generated modid field as well
• Mod template generator: various improvements #35 Switched out the tab char's for spaces, I can reset this one if we don't like the change but it is more standard for Java IIRC
• Mod classpath group name is hard coded to "modid" #36 Use a "$modId" for the classPath Group in gradle. Using the quotes should allow for more room for more abnormal mod names.