[#85] Fixes bug on version switcher

Introduced in https://github.com/IATI/IATI-Public-Validator/commit/a1884ca7a5e62ffb630829acd012228941e1f0a0
[#84] Fixes bug whereby elements not found on 2.01 files are not shown

This was because of the way the new 2.01 schema is structutred.
When we get all eleemnts from the schema we need to use different
xpath expressions for version 2.x compared to version 1.x
Merge pull request #86 from IATI/85-version-switcher-bug

[#85] Fixes bug on version switcher
Merge pull request #87 from IATI/84-did-not-find-bug

[#84] Fixes bug whereby elements not found on 2.01 files are not shown
Merge pull request #88 from IATI/master

Move recent bug fixes into live branch