#160: Write unit tests for SQLDatabaseUtils

[aaronhktan]

Description

This commit adds unit tests that test version upgrade functionality, as well as dictionary import functionality.

Part of a series of commits for #160.

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Tested on all three platforms.

PASS	Executing test case TestSqlDatabaseUtils
	Qt version: 5.15.2
	Qt build: Qt 5.15.2 (x86_64-little_endian-lp64 shared (dynamic) release build; by GCC 5.3.1 20160406 (Red Hat 5.3.1-6))
	QTest version: 5.15.2
PASS	Executing test function initTestCase
PASS	TestSqlDatabaseUtils::initTestCase
	Execution took 0.259449 ms.
PASS	Executing test function updateDatabaseFromV1
PASS	TestSqlDatabaseUtils::updateDatabaseFromV1
	Execution took 49.8147 ms.
PASS	Executing test function updateDatabaseFromV2
PASS	TestSqlDatabaseUtils::updateDatabaseFromV2
	Execution took 44.7733 ms.
PASS	Executing test function addAndRemoveSources
PASS	TestSqlDatabaseUtils::addAndRemoveSources
	Execution took 53.7935 ms.
PASS	Executing test function readSources
PASS	TestSqlDatabaseUtils::readSources
	Execution took 33.3397 ms.
PASS	Executing test function cleanupTestCase
PASS	TestSqlDatabaseUtils::cleanupTestCase
	Execution took 0.001573 ms.
	Test execution took 182.273 ms.

Checklist:

• My code follows the style guidelines of this project (black for Python
  code, .clang-format in the src/jyut-dict directory for C++)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have translated my user-facing strings to all currently-supported languages
• I have made corresponding changes to the documentation