Refactor CveDB

- make class thread-safe and declare so (also DatabaseProperties)
- prepared statements represented by enum: performance gain, eases experiments when tuning for performance
- minor changes/cleanup/code style

dependency-check-core/src/main/resources/data/dbStatements.properties

@@ -19,6 +19,7 @@ DELETE_REFERENCE=DELETE FROM reference WHERE cveid = ?
 DELETE_SOFTWARE=DELETE FROM software WHERE cveid = ?
 DELETE_VULNERABILITY=DELETE FROM vulnerability WHERE id = ?
 CLEANUP_ORPHANS=DELETE FROM cpeEntry WHERE id not in (SELECT CPEEntryId FROM software);
+COUNT_CPE=SELECT COUNT(*) records FROM cpeEntry
 INSERT_REFERENCE=INSERT INTO reference (cveid, name, url, source) VALUES (?, ?, ?, ?)
 INSERT_SOFTWARE=INSERT INTO software (cveid, cpeEntryId, previousVersion) VALUES (?, ?, ?)
 INSERT_CPE=INSERT INTO cpeEntry (cpe, vendor, product) VALUES (?, ?, ?)
@@ -38,6 +39,6 @@ INSERT_PROPERTY=INSERT INTO properties (id, value) VALUES (?, ?)
 UPDATE_PROPERTY=UPDATE properties SET value = ? WHERE id = ?
 DELETE_PROPERTY=DELETE FROM properties WHERE id = ?
 
-#the following two statements are unused and are only referenecd in dead code
+#the following two statements are unused and are only referenced in dead code
 DELETE_UNUSED_DICT_CPE=DELETE FROM cpeEntry WHERE dictionaryEntry=true AND id NOT IN (SELECT cpeEntryId FROM software)
 ADD_DICT_CPE=MERGE INTO cpeEntry (cpe, vendor, product, dictionaryEntry) KEY(cpe) VALUES(?,?,?,true)