Add documentation for some of the features recently added to Semgrex and Ssurgeon

Author: AngledLuffa

src/edu/stanford/nlp/semgraph/semgrex/SemgrexPattern.java

@@ -53,6 +53,16 @@
  * The special case of an empty text can be tested for with an empty regex.
  * For example, words marked with {@code SpaceAfter=no} will have a blank {@code after} attribute.
  * {@code {after://}} will search for this.
+ * <br>
+ * It is now also possible to negate individual attributes in Semgrex with {@code !:}
+ * For example, this expression will search for a NOUN which is not "boy":
+ * {@code {lemma!:boy;pos:NOUN}}
+ * <br>
+ * Attributes which are maps, in particular the morphological
+ * features, can be searched by writing a map, such as
+ * {@code {morphofeatures:{Tense:Past;Person!:3}}}
+ * This expression will
+ * search for words which are past tense but are not in 3rd person.
  * <h3>Relations</h3>
  *
  * Relations are defined by a symbol representing the type of relationship and a

src/edu/stanford/nlp/semgraph/semgrex/ssurgeon/Ssurgeon.java

@@ -140,6 +140,7 @@
  *   {@code -updateMorphoFeatures ...} will edit or add the features without overwriting existing features.
  *   TODO: if anyone needs the ability to remove features without resetting the entire features map,
  *   please file an issue on github.
+ *   {@code -remove ...} will remove the attribute entirely, such as doing {@code -remove lemma} to remove the lemma.
  *</p><p>
  * {@code lemmatize} will put a lemma on a word.
  * {@code -node} is the node to edit.