Fix compact singular formats and patterns with no numbers

[DenverCoder1]

Fixes #931

• Adds support for patterns with no numbers
• In compact format, only uses "one" format if the number pluralizes to "one" before rounding
• In compact format, explicit "1" formats can now be applied (there seem to be none with explicit "0" formats)

>>> numbers.format_compact_decimal(1000, format_type='long', locale='it')
'mille'  # previously 'mille1'
>>> numbers.format_decimal(1, format="mille")
'mille'  # previously 'mille1'
>>> format_compact_decimal(21098765, format_type="long", locale="mk")
'21 милиони'  # previously '21 милион' (would still be singular if the number were 21000000)
>>> numbers.format_compact_decimal(1000, format_type='long', locale='fr')
'mille'  # previously '1 millier'

[codecov]

Codecov Report

Merging #932 (0713d3a) into master (a45e25e) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #932      +/-   ##
==========================================
+ Coverage   91.55%   91.57%   +0.01%     
==========================================
  Files          21       21              
  Lines        4241     4247       +6     
==========================================
+ Hits         3883     3889       +6     
  Misses        358      358              

Impacted Files	Coverage Δ
babel/numbers.py	97.97% <100.00%> (+0.03%)	⬆️

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[akx]

Thanks!