Make offset and amplitude handling of the Tabor AWG configurable

[lankes-fzj]

The Tabor AWG has a new attribute "amplitude_offset_handling". Now it is possible to consider the offset when uploading a program to the instrument.

This pull request belongs to #446

[coveralls]

Pull Request Test Coverage Report for Build 1743

• 16 of 18 (88.89%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.006%) to 93.624%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qupulse/hardware/awgs/base.py	11	12	91.67%
qupulse/hardware/awgs/tabor.py	5	6	83.33%

Totals
Change from base Build 1741:	0.006%
Covered Lines:	4811
Relevant Lines:	5070

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 1743

• 16 of 18 (88.89%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.006%) to 93.624%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qupulse/hardware/awgs/base.py	11	12	91.67%
qupulse/hardware/awgs/tabor.py	5	6	83.33%

Totals
Change from base Build 1741:	0.006%
Covered Lines:	4811
Relevant Lines:	5070

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 1747

• 17 of 18 (94.44%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 93.723%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qupulse/hardware/awgs/base.py	11	12	91.67%

Totals
Change from base Build 1741:	0.1%
Covered Lines:	4815
Relevant Lines:	5070

---

💛 - Coveralls