Use extended brackets instead of box-drawing characters in log messages

[waldyrious]

(Opening a PR in my fork to test the Travis build.)

This change is to propose using extended brackets instead of box-drawing characters in multi-line log messages. The box-drawing characters were first introduced in JuliaLang#25111.

This change would have two advantages for multi-line log messages:

• They would become semantically consistent with the single-line log messages (which use the left bracket character, [)
• They would become more visually consistent with the single-line log messages, since the box drawing characters ┌ and └ have the horizontal section in the middle of the line, rather than at the top and the bottom like [
• Due to the previous point, the characters would produce a left-flanking box that actually "wraps" the log message, rather than be slightly shorter than the text.

Examples (based on this PR)

Current:

# Characters used:
# - Box Drawings Light Down and Right, U+250C
# - Box Drawings Light Vertical, U+2502
# - Box Drawings Light Up and Right, U+2514

┌ Info: parameters:
│   {UUID} = UUID("1a7ac041-bdf1-4da1-9e3a-91f6f6c88e92")
│   {PKGNAME} = "Foo"
│   {USERNAME} = "John Doe"
│   {USEREMAIL} = "[email protected]"
│   {GHUSER} = "jdoe"
└   {YEAR} = 2019
Confirm (Y)> 
[ Info: copy and substitute

Proposed:

# Characters used:
# - Left Square Bracket Upper Corner, U+23A1
# - Left Square Bracket Extension, U+23A2
# - Left Square Bracket Lower Corner, U+23A3

⎡ Info: parameters:
⎜   {UUID} = UUID("1a7ac041-bdf1-4da1-9e3a-91f6f6c88e92")
⎜   {PKGNAME} = "Foo"
⎜   {USERNAME} = "John Doe"
⎜   {USEREMAIL} = "[email protected]"
⎜   {GHUSER} = "jdoe"
⎣   {YEAR} = 2019
Confirm (Y)> 
[ Info: copy and substitute

[waldyrious]

An alternative to make the printing of logs more consistent could be to go the other way and replace [ for single-line log messages with a simple hyphen -, or more appropriately, ╶:

# Characters used:
# - Box Drawings Light Down and Right, U+250C
# - Box Drawings Light Vertical, U+2502
# - Box Drawings Light Up and Right, U+2514
# - Box Drawings Light Right, U+2576

┌ Info: parameters:
│   {UUID} = UUID("1a7ac041-bdf1-4da1-9e3a-91f6f6c88e92")
│   {PKGNAME} = "Foo"
│   {USERNAME} = "John Doe"
│   {USEREMAIL} = "[email protected]"
│   {GHUSER} = "jdoe"
└   {YEAR} = 2019
Confirm (Y)> 
╶ Info: copy and substitute

But honestly I prefer the first approach to this one.