Improve footnotes on LaTeX

[tk0miya]

There are some themes to improve footnotes on LaTeX

• numbering rule of footnotes; manually numbered footnotes and auto numbered
• scope of footnote numbers (per chapter, per section, per page and so on)
• position of footnotes defined inside admonitions
• switching footnote counter (cf. a, b, c...) in adomonitions (discussed in make latexpdf and hiperlinks: "LaTeX Error: Counter too large." #2530)
• making working hyperlinked (clickable) footnotes from code captions, from inside tables, etc.

[jfbu]

also the problem of allowing code-blocks in footnotes.

edit: this was fixed at b8e0e93 (Sphinx 1.5)

[jfbu]

also the issue that sometimes there is a space token before the footnote in the LaTeX file, sometimes (in particular for automatically generated footnotes from using latex_show_urls = 'footnote') there is none.

edit: this was fixed at 828c96e (#3057) (Sphinx 1.5)