Language Server integration should respect empty LS capabilities

[evidolob]

According to spec of ServerCapabilities object all LS capabilities are optional.
We should respect that. For now we have NPE when LS don't provide textDocumentSync :

TextDocumentSynchronizeFactory.java:40 Uncaught (in promise) TypeError: Cannot read property 'ordinal_0' of undefined(…)getSynchronize@
 TextDocumentSynchronizeFactory.java:40
 LanguageServerReconcileStrategy@ LanguageServerReconcileStrategy.java:43
 org$eclipse$che$plugin$languageserver$ide$editor$LanguageServerReconcileStrategy_org$eclipse$che$plugin$languageserver$ide$editor$LanguageServerReconcileStrategy_methodInjection_ @ org_eclipse_che_ide_client_inject_IDEInjector_IDEInjectorGinjector_fragment.java:164
 assistedInject_buildKey$type$org$eclipse$che$plugin$languageserver$ide$editor$LanguageServerReconcileStrategyFactory$_annotation$$none$$ @
 org_eclipse_che_ide_client_inject_IDEInjector_IDEInjectorGinjector_fragment.java:168
 build_7 @ org_eclipse_che_ide_client_inject_IDEInjector_IDEInjectorGinjector_fragment.java:152
 LanguageServerEditorConfiguration @ LanguageServerEditorConfiguration.java:65
 org$eclipse$che$plugin$languageserver$ide$editor$LanguageServerEditorConfiguration_org$eclipse$che$plugin$languageserver$ide$editor$LanguageServerEditorConfiguration_methodInjection_ @ org_eclipse_che_ide_client_inject_IDEInjector_IDEInjectorGinjector_fragment.java:88
 assistedInject_buildKey$type$org$eclipse$che$plugin$languageserver$ide$editor$LanguageServerEditorConfigurationFactory$_annotation$$none$$ @ org_eclipse_che_ide_client_inject_IDEInjector_IDEInjectorGinjector_fragment.java:92build_6 @ org_eclipse_che_ide_client_inject_IDEInjector_IDEInjectorGinjector_fragment.java:76
 apply_1003 @ LanguageServerEditorProvider.java:98
 apply_1004 @ LanguageServerEditorProvider.java:96
 (anonymous function) @ JsPromise.java:78