Improve the documentation

[spl0k]

• [x] Convert existing docs to reStructuredText
• [x] Rewrite the installation process, possibly splitting database setup in other doc(s)
• [x] Add a page describing the daemon
• [x] Properly document web deployment options
• [x] Simplify the README
• [x] Try to install the manpages along the software

Once done, publish on ReadTheDocs.

[codecov[bot]]

Codecov Report

Merging #206 (7833726) into master (0b67aeb) will decrease coverage by 0.05%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #206      +/-   ##
==========================================
- Coverage   88.53%   88.47%   -0.06%     
==========================================
  Files          35       35              
  Lines        3358     3359       +1     
==========================================
- Hits         2973     2972       -1     
- Misses        385      387       +2     

Impacted Files	Coverage Δ
supysonic/covers.py	80.39% <0.00%> (-3.93%)	:arrow_down:
supysonic/api/unsupported.py	100.00% <0.00%> (ø)

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