API to preprocess template names

[s2b]

Currently, Fluid preprocesses the supplied template names by requiring the first character of the name to be uppercase. We could introduce an API which allows Fluid users to change this behavior. We might also introduce breaking behavior later on, where we remove the uppercase-requirement from Fluid's standard implementation altogether.

The described API will probably located in the already existing TemplatePaths class and could then be overwritten by Fluid integrations if different behavior is desired (like providing fallbacks from first-character-uppercase to first-character-lowercase).

[s2b]

Related: #371