[ASTERIXDB-2979][MTD][GRAPH] Implement CREATE / DROP GRAPH

Initial commit. This supports CREATE GRAPH, DROP GRAPH, and prevents
dropping views / functions / datasets / synonyms / dataverses that a
graph depends on.

Change-Id: Ibaf4dc7066b85d8ea3b58c6b90fd83af3a700506
Reviewed-on: https://asterix-gerrit.ics.uci.edu/c/asterixdb-graph/+/14644
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Ian Maxon <imaxon@uci.edu>
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..a546fd6
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,12 @@
+opttest
+target
+build
+
+.classpath
+.settings
+.project
+.idea
+.DS_Store
+
+*.swp
+*.iml
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