Escaping reserved characters

[jobol]

Add an escaping character for protecting reserved characters. Doing thing could solve corner case issues:

• key starting with one of the characters used for section, partial, ... (/^#< ...)
• the question of the dot (see Add test case for dotted names #180)
• for possible extensions (see ex: https://gitlab.com/jobol/mustach#value-testing-equality-mustach_with_equal)

The character \ is a good candidate.

For example, a.b could address the field b in a where a\.b address the field a.b.

Other example {{\#main}} access the field #main.

[agentgt]

I think this is a good idea and had similar thoughts. If we add power filters #153 I think we should consider adding some escaping. The tag names data has been kind of dangerously undefined and I think it is going to bite us in the long run.

EDIT I will add such change IMO would have to be a 2.0 change.