Added fixed width source adapter

[LeonB]

Config can be like this:

<source model="ho_import/source_adapter_fixedwidth">
    <file>var/import/fixedwidth.txt</file>

    <trim>1</trim>
    <columns>
        <col1>8</col1>
        <col2>4</col2>
        <col3>12</col3>
        <col4>13</col4>
        <col5>27</col5>
        <col6>5</col6>
        <col7>4</col7>
        <col8>9</col8>
        <col9>4</col9>
        <col10>18</col10>
        <col11>20</col11>
        <col12></col12> <!-- to end of line -->
    </columns>
</source>

This will be the data generated based on fixedwidth.txt.

+-------+------------+
| key   | 0          |
+-------+------------+
| col1  | 16524      |
| col2  | 01         |
| col3  | 10/17/2012 |
| col4  | 3930621977 |
| col5  | TXNPUES    |
| col6  | S1         |
| col7  | Yes        |
| col8  | RHMXWPCP   |
| col9  | Yes        |
| col10 |            |
| col11 | 5,007.10   |
| col12 | No         |
+-------+------------+