Update generic_test_mechanism.xsd

Fixing #134.
Make Description, Type and Specification elements optional
Remove duplicate nested sequences from Campaign #143
The Source element in SightingType should be of InformationSourceType not StructuredTextType #138
The Source element of ConfidenceType should be of InformationSourceType not ControlledVocabularyStringType #157
The Source element of StatementType should be of InformationSourceType
not ControlledVocabularyStringType #161
Annotations for AssetTypeType are incorrect #144
"Degredation" - Typo in Vocab Value in AvailabilityLossType #153
Merge pull request #155 from STIXProject/issue_134

Update generic_test_mechanism.xsd, fixes #134
Merge pull request #156 from STIXProject/issue_143

Remove duplicate nested sequences from Campaign, fixes #143
Merge pull request #158 from STIXProject/issue_138

The Source element in SightingType should be of InformationSourceType, fixes #138
Merge pull request #169 from STIXProject/issue_152

Indicator => Campaign reference appears to be broken, fixes #152
Merge pull request #163 from STIXProject/issue_157

The Source element of ConfidenceType should be of InformationSourceType, fixes #157
Merge pull request #170 from STIXProject/issue_161

The Source element of StatementType should be of InformationSourceType, fixes #161
Merge pull request #166 from STIXProject/issue_144

Corrects annotations on AssetTypeType, fixes #144
Merge branch 'version_1.1.1', remote-tracking branch 'origin' into version_1.1.1
fix incorrect change to the version of DiscoverMethod
Merge pull request #168 from STIXProject/issue_153

Corrects typo in AvailabilityLossVocabType-1.0, fixes #153
Merge remote-tracking branch 'origin/version_1.1.1' into version_1.1.1
add test case for #134
- Change version attribute on the root “xs:schema” element to x.x.1
- Change <version> annotation inside the “xs:appinfo” element ot x.x.1
- <date> annotation inside the “xsi:appinfo” element to 5/1/14
- For STIXType and each of the 7 components, we need to update the
	*VersionType enumeration, adding x.x.1