UPGRADE

Upgrade FROM 0.2 to 0.3

The method increase of Version is renamed to getNextIncreaseOf.
The VersionValidator has been renamed to ContinuesVersionsValidator.
The ContinuesVersionsValidator has api changed to separate the validation from providing suggestions.

Before:
```
VersionsValidator::isVersionContinues($versions, Version::fromString('v0.2.0'), $possibleVersions);
```
After:
```
$validator = new ContinuesVersionsValidator(...$existingVersions); // Expects the versions as a variadic arguments

$result = ContinuesVersionsValidator::isContinues(Version::fromString('v0.2.0'));
$possibleVersions = $validator->getPossibleVersions(); // Must be called after isContinues(), otherwise empty
```
Note: The suggested versions did not take existing versions into account.

Now, instead if a newer major or minor version already exists it only allows a patch release for the bounded minor version. If both 1.1 and 2.0 exist then 1.2 is no longer suggested, nor considered an acceptable increment.

Otherwise all possible suggestions are accepted.