Support for mzIdentML 1.0

Added support for mzIdentML 1.0 - had to update all the mzID... constructors. Mainly minor updates of the form 
```c
.path <- getPath(ns)
paste0(.path, "/x:.../)
```
except for mzIDevidence, where I needed to specify a specific path for PeptideEvidence.

Bumped version to 0.3.0. Have not re-run roxygen.