Fixes #1275. Fixes pom dynamic revision conversion

Fixes #1275

Ivy and pom uses slightly different notation for version range and dynamic revision. This change fixes the dynamic revisions involving “+”.

First, when a revision like “1.1+” is found, it will now be treated as “1.+”.
Next, when it finds a revision like “1+” is found, it will be treated as “+”. The conversion of “+” is hardcoded to be “[0,)”.

- http://ant.apache.org/ivy/history/2.3.0/ivyfile/dependency.html
- http://maven.apache.org/enforcer/enforcer-rules/versionRanges.html

/review @havocp 
other cases I can think of: just `+` by itself, `somejunk +`, `wedontunderstandthis`