fix some typos
delete trailing whitespaces
Add consitency by using Verb (infinitive uppercased) and not
verbs (conjugated lowercased).
fix with @code{} when needed
Fix Gnuplot and GnuCash syntax accodingly first page of web site.
Fix url
fix emphasis
fix double quotes
suppress double spaces before ':' and ','
Merge pull request #180 from thdox/documentation-typos

Documentation typos
M-x texinfo-every-node-update
Moves payees from end to after accounts
Add some help before release. Copied from texinfo.texi.
Add new index for options
Add blank line before @table and after @end table as recommanded in Tips
section of Texinfo manual.
Around section's commands, add a blank line as recommanded in section
Tips of Texinfo manual.
Add @node when missing
modified -- to --- as texinfo will use two -- in Info and a long - for TeX.
Improves acprep python3 compatibility

Replaces string.join with str.join
Forces conversion to str from byte-returning functions
Introduces usage of 'as' keyword when catching exception instances
Replaces has_key with usage of the 'in' keyword for dictionary key presence checking.
Fill paragraph with alignment on 70th column