Document how to properly deal with exceptions in macros

In our control room our operators started using macros for the accelerators operation. They migrated a set of python scripts into macros. We have observed that in their scripts (now macros) they were using broad exception types in the except clause. This may interfer with the macro stopping/aborting. 484af30b warns about it.

Since the How to develop macros documentation already growed to a big chapter I take a profit of this PR to add a table of contats (TOC) in order to faciltate navigation. The section headers are now links to the chapter in the TOC. It looks more or less like this:

@sardana-org/integrators could you please take a look on this. Thanks a lot!