#28: Refactor for better organization and class names

[benedeki]

• no logical changes, only moves and class renames
• Removed DB prefix from all DBItem classes (e.g. DBTable -> Table)
• structured folders following the same sub-structure
• joined DBSchema and SchemaDef

Closes #28

[github-actions[bot]]

JaCoCo code coverage report - scala 2.12.18

File	Coverage [23.97%]	:x:
DBTableFromYaml.scala	100%	:green_apple:
TableColumn.scala	100%	:green_apple:
TransactionGroup.scala	100%	:green_apple:
FunctionDrop.scala	96.15%	:green_apple:
PgTableFileParser.scala	92.59%	:green_apple:
UserCreation.scala	88.89%	:green_apple:
package.scala	79.17%	:x:
PgFunctionFileParser.scala	78.59%	:x:
package.scala	78.26%	:x:
package.scala	64.41%	:x:
package.scala	64.29%	:x:
package.scala	64.29%	:x:
GenericFileParser.scala	50%	:x:
TableIndex.scala	43.51%	:x:
FunctionFromSource.scala	38.24%	:x:
MapImplicits.scala	33.33%	:x:
TableDef.scala	24.3%	:x:
FileReader.scala	20.73%	:x:
SchemaDef.scala	0%	:x:
FunctionFromPG.scala	0%	:x:
TableCreation.scala	0%	:x:
TableEntry.scala	0%	:x:
TableOwnership.scala	0%	:x:
TableIndexDrop.scala	0%	:x:
TablePrimaryKeyAdd.scala	0%	:x:
TablePrimaryKeyDrop.scala	0%	:x:
TableIndexCreation.scala	0%	:x:
package.scala	0%	:x:
SqlExecutor.scala	0%	:x:
TableColumnDefaultSet.scala	0%	:x:
TableColumnAdd.scala	0%	:x:
TableColumnNotNullDrop.scala	0%	:x:
TableColumnCommentDrop.scala	0%	:x:
TableColumnCommentSet.scala	0%	:x:
TableColumnDrop.scala	0%	:x:
TableColumnDefaultDrop.scala	0%	:x:
FunctionOwnership.scala	0%	:x:
FunctionBody.scala	0%	:x:
FunctionGrant.scala	0%	:x:
FunctionEntry.scala	0%	:x:
CliParser.scala	0%	:x:
SchemaUserParser.scala	0%	:x:
Ultet.scala	0%	:x:
TaskConfig.scala	0%	:x:
DBTableFromPG.scala	0%	:x:
SchemaGrant.scala	0%	:x:
SchemaOwnership.scala	0%	:x:
SchemaCreation.scala	0%	:x:
TableInsert.scala	0%	:x:
TableAlter.scala	0%	:x:
DatabaseDef.scala	0%	:x:
DBItem.scala	0%	:x:
DBAppModel.scala	0%	:x:
SetImplicits.scala	0%	:x:
UserDef.scala	0%	:x:

Total Project Coverage	22.55%	:green_apple: