Display units on attributes

[only1chunts]

User story

As a submitting author
I want to be able to provide the units associated with my sample attributes
So that users know which units are used for each attribute

Acceptance criteria

Given I am submitting a sample with metadata in the submission wizard
When I provide an attribute value that requires a unit to be defined
Then I am given an appropriate dropdown menu of unit choices to select from

Additional information

we don't want the entrie list of unit to appear in the drop-down, only the unit allowed for a particular attribute type.

There is a allowed_units field in attribute table, but is text, and we can parse it fo id of units, probably better adding a table allowed_units`` linking unit and attribute.

Is your feature request related to a problem? Please describe.
Currently we have the ability to record units of attributes in the database, but this information is not presented in either the user interface or the admin interface. Because its not displayed many of the attribute values also contain the units either as well or instead of in the units column. Before we tidy that up in the database we should make the units visible to users & admin.

Describe the solution you'd like
On the dataset pages the sample attribute and file attribute fields should include the units of values IF the units have been provided.
If this update is made with no other changes to the current (user) display then that is as simple as concatenating the units to the value. If there are other changes made to the current display then those changes will need to be taken into consideration.
For the Admin pages the units need to be incorporated as per ticket #54 in the same way its done in the WhiteLabel submission wizard.

Additional context
This should be done in conjunction with the admin sample view ticket #54, and any other works planned on the UI for datasets.