Fix README and some translation strings

[patrickrobrecht]

1. Simplify the description in the README (including the changes from Fix declaration of WP compatiblity of AntiVirus 1.4.0 #84 merged into stable)
2. Remove coderisk link from main plugin file
3. Fix some translation strings which contain spelling mistakes or are inconsistent
4. Remove FAQ section in the README and the link to the FAQ on the settings page (everything should be in the documentation now, the only question should be answered in the normal text now)

(Change 2 has been pushed to the 1.4.0 tag on SVN manually to trigger the import of the files after merging #84.)

[stklcode]

LGTM

[codecov-io]

Codecov Report

Merging #85 (0f5f72a) into develop (2191d79) will increase coverage by 0.25%.
The diff coverage is 44.44%.

@@              Coverage Diff              @@
##             develop      #85      +/-   ##
=============================================
+ Coverage      26.25%   26.51%   +0.25%     
  Complexity       147      147              
=============================================
  Files              5        5              
  Lines            518      513       -5     
=============================================
  Hits             136      136              
+ Misses           382      377       -5     

Impacted Files	Coverage Δ	Complexity Δ
antivirus.php	0.00% <ø> (ø)	0.00 <0.00> (ø)
inc/class-antivirus.php	13.22% <0.00%> (+0.20%)	83.00 <0.00> (ø)
inc/class-antivirus-safebrowsing.php	91.30% <75.00%> (ø)	9.00 <0.00> (ø)
inc/class-antivirus-checksumverifier.php	89.83% <100.00%> (ø)	17.00 <0.00> (ø)

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