Well I'm not actually certain which gradle you have, I can only tell by looking at a certain filename. However it has literally just occured to me that said file could be imported from the Flan's source...
Either way you've mismatched the versions (as evidenced by every file causing errors), changing either side should fix it.
Try reinstalling 1.7.10 gradle.
EDIT: I don't see how that can be 1.7 Flan's mod, I can see files and folders that are only in 1.8 version (renderhack ect.) Unless Flan's completely cocked up the github repo... Unless you've put the wrong version in then tried to overwrite it with the other one. In which case you need to reinstall gradle.
Stephen King wrote: “Don't ask me silly questions
I won't play silly games
I'm just a simple choo choo train
And I'll always be the same"