Enable per file verification configuration

[franck44]

Some files need custom verification options to be checked efficiently.
It would be nice if the batch processing (script verifyAll.sh) could run the verification of each file with a default/custom verification configuration.

[franck44]

Idea:
add a line in each file e.g. @dafny some verification config options
Add a default config in the script: if a file has a line @dafny use custom config otherwise use default.

Safe config.
We should also provide the ability to force running the verification. That would mean forcing /dafnyVerify:1 and
/noCheating:1.

[franck44]

Integrated in verifyAll.sh and seems to be working.