Created contextual and rule using pattern matcher
Split contextualize-and-rule in two patterns

One applies when the relation is an EvaluationLink, the other one applies in all other cases.
Renamed rules
Added contextualize-subset-rule
Renamed contextualize file as it contains both 'and' and 'subset' patterns now
Added decontextualize patterns
Added wiki links, slight modifications
Changed VariableNode to ImplicationLink, added Inheritance

As per p. 234 in the PLN book
Replaced VariableNode with EvaluationLink
Replaced ImplicationLink with InheritanceLink

As per the recommendation by Ben, as an AndLink between ConceptNodes represents their intersection
Added example sentences/links
Created file with simple test examples using pattern matcher context rules
Modified explanation of context rules
Modified contextualize-subset so superfluous ListLinks aren't produced

As suggested by Linas in issue #844
Slightly changed rules to avoid redundance in output
Corrected link
Modified/corrected decontextualize rules
Added input/output test examples for decontextualize rules
Slight changes to contextualize rules
Fixed indentation