moving some memory allocation to init function rather than within

execution cycles and fixing test db tear down so that it drops
checked_headers table instead of individual columns (droping columns
only hides them, they remain in memory and continue to contribute to the
1600 column limit which causes us to eventually exceed it)

pkg/omni/shared/parser/parser.go

@@ -93,7 +93,7 @@ func (p *parser) lookUp(contractAddr string) (string, error) {
 
 // Returns only specified methods, if they meet the criteria
 // Returns as array with methods in same order they were specified
-// Nil wanted array => no events are returned
+// Nil or empty wanted array => no events are returned
 func (p *parser) GetSelectMethods(wanted []string) []types.Method {
 	wLen := len(wanted)
 	if wLen == 0 {