[FIX] web: fix onchange_spec computation
[REV] Undo 29a9c1, causes endless loop during db creation, to be fixed
[FIX] account_asset: remove nonsensical o2m declaration on account.move.line
[FIX] fleet: remove nonsensical @ondelete on one2many field declaration
[IMP] point_of_sale: unused imports
[FIX] fields.Binary read: restore compatibility with old bin_size API

We used to return the "bin_size" version of a binary field
using a human-readable format with both a value and a unit
of measure. Some heuristics in the web client depend on it
and we can easily mimic that behavior using the new
implementation.
In addition we can continue to support the more specific
`bin_size_<field>` context key to selectively turn
bin_size on per-field.

Finally, the new implementation depends on the
pg_size_pretty() PostgresSQL function that changed in
PG 9.2 in a somewhat incompatible manner. So we force
the ::bigint cast to avoid errors in 9.2+.
See also:
http://postgresql.1045698.n5.nabble.com/No-pg-size-pretty-numeric-was-not-such-a-hot-idea-td5710106.html
[IMP] orm/models, fields: new @copy attribute for fields, o2m not copied by default!

Introduction of a new `copy` attribute for all fields,
both in the new and old API. Depending on the value
of this attribute, the field will be copied or discared
during a record copy() operation.

The value of `copy` defaults to True for all fields
except computed fields (`fields.function` in the old
API, or any field witth a `compute` attribute in the
new API) and one2many fields (fields.one2many /
fields.One2many), which both default to False.

This represents an important change for One2many fields,
as they used to be copied by default. This was a source
of dangerous bugs, as one2many fields do not always
represent composition/ownership relationships.
When they do not, duplicating the o2m lines often
lead to unwanted duplication of other records.

As of v8 one2many copy will be opt-in, so any declaration
of a one2many field that should be copied (typically
a "line" object) will have to be explicitly done
with copy=True:

 line_ids = fields.One2Many(order.line, order_id, string="Lines", copy=True)

For all other fields, `copy=False` can be used
to easily reset/skip the field during duplication.
This is something that used to require an explicit
override of the copy() method.

All modules/apps were updated to add an explicit
copy=True parameter for one2many fields that do need
to be copied (e.g. Sales Order lines, etc.).
Whenever possible overridden copy/copy_data
methods were dropped and replaced by extra
`copy=False` parameters.