This commit adds 2 major module for handling SIE4 files within Odoo.

Even though the SIE5 is already available in Odoo, the majority of the Swedish userbase still uses SIE4 (or below) for importing and exporting accounting data.

In addition to the new features below, this commit also renames the current odoo implementation of SIE5 from just "SIE" to "SIE 5" to avoid confusion between the two.

This first implementation does not at all consider the effects of the `#OBJEKT` and `#DIM` (or other similar dimension) items.

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### SIE4 Import - `l10n_se_sie4_import`

Odoo can now import accounting data from SIE of type 4 and below (thanks to backward-compatibility of SIE format).

SIE4 files are designed as a text file with label on each line and its contents. One item can be referred by another item down the file, so we need a variable (`data_map`) to save the required information for future use, in-between the reading process.

From the SIE4 file, we can then import the following data: company, chart of accounts, fiscal year, and move informations.

An option will be provided when creating the wizard to allow user to choose whether they'd like to import opening balance move, and/or update any duplicate accounts already found in their company with the one in the file.

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### SIE4 Export - `l10n_se_sie4_export`

Odoo's implementation of exporting SIE4 files are placed in the General Ledger view's export buttons, similar to other import implementation like SAF-T and Libros.

To be able to export SIE4 file, the date periods in the selected options must be of type fiscal year, and exporting multiple companies at once is forbidden.

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[SIE 4 documentation](https://sie.se/wp-content/uploads/2020/05/SIE_filformat_ver_4B_ENGLISH.pdf)

task-id: 3735808