Always throw exceptions rather than sometimes returning false

[rrigby]

This will require a closer look, but I've been using these changes for a while with success.

Reasoning:
In most situations a problem with a query resulted in picodb's SQLException propagating out making for easy handling.
Here's the source of the exception in picodb for reference:

   // StatementHandler.php   

    public function execute()
    {
        try {
            $this->beforeExecute();

            $pdoStatement = $this->db->getConnection()->prepare($this->sql);
            $this->bindParams($pdoStatement);
            $pdoStatement->execute();

            $this->afterExecute();
            return $pdoStatement;
        } catch (PDOException $e) {
            return $this->handleSqlError($e);
        }
    }

    public function handleSqlError(PDOException $e)
    {
        $this->cleanup();
        $this->db->cancelTransaction();
        $this->db->setLogMessage($e->getMessage());

        throw new SQLException('SQL Error: '.$e->getMessage());
    }

However in some situations, this exception is caught in picomapper and instead false is returned. This makes handling errors more difficult. The most common situation I encountered this, was when I had a bug and was attempting to update an aggregate with new duplicate child records. It would attempt to insert a duplicate child and that resulting exception would be caught and false would be returned. I was confused why my request was succeeding but my record wasn't updating. After diving in I figured out why, and thus this PR 😅
before:

    } catch (\Exception $e) {
        if ($useTransaction) {
            $this->db->cancelTransaction();
        }

        return false;
    }

after:

    } catch (\Exception $exception) {
        if ($useTransaction) {
            $this->db->cancelTransaction();
        }

        throw $exception;
    }

---

I've also opted to simply remove the returning false. Such as this example:

    if (!parent::insert($base)) {
            // Transaction already cancelled by the statement handler
            return false;
    }

In the above example false is never returned, as the SQLException from picodb is thrown already. So I've simply replaced it with:

parent::insert($base);

---

I've also escalated to exception any errors in the picomapper library that previously returned false, for example:
before:

    if (!$original = $this->findOne()) {
        return false;
    }

after:

    if (!$original = $this->findOne()) {
        throw new \Exception('Failed to update record. Original not found.');
    }

Maybe these should use a specific exception class from picomapper, I'm happy to add that if you have thoughts. I'd just kept it simple for now.

[rrigby]

This test simply confirms existing behaviour, that it's fine to include duplicate items in the update array, as just the last entry for a given id will be applied to the item in the db.