Redeem HTLC can't handle binary (hex encoded) preimages

**Describe the bug**
The redeem HTLC preimage text box assumes the preimage is an ascii string. For HTLCs which used a binary preimage, there is no way to supply the preimage.

**To Reproduce**
Steps to reproduce the behavior:
1. Create an HTLC where the hash is the hash of a binary preimage
2. In recipient's account, go to Spotlight --> HTLC
3. Click "Redeem" next to the HTLC
4. Observe inability to supply binary preimage

**Expected behavior**
Expected would be an option to indicate the encoding of the preimage. (E.g. "ascii", "hex", etc.)

**Screenshots**
If applicable, add screenshots to help explain your problem.

**Desktop (please complete the following information):**
- OS: MacOS
- Browser Electron App
- Version 191120

Start at the Spotlight → HTLC redeem flow described in the reproduction steps and trace how the preimage text is collected and submitted. The work is done when the redeem interface lets users identify an encoding such as ASCII or hex and successfully supplies binary preimages for redemption.

Written by the indexing model from the issue text.