Change some args to italics instead of bold, and use singular aliases

Also remove columns (i) alias for now.

Co-Authored-By: Dongdong Tian <[email protected]>

pygmt/base_plotting.py

@@ -606,11 +606,11 @@ def grdview(self, grid, **kwargs):
 
  @fmt_docstring
  @use_alias(
- A="straight_lines",
+ A="straight_line",
  B="frame",
  C="cmap",
  D="offset",
- E="error_bars",
+ E="error_bar",
  F="connection",
  G="color",
  I="intensity",
@@ -625,7 +625,6 @@ def grdview(self, grid, **kwargs):
  X="xshift",
  Y="yshift",
  Z="zvalue",
- i="columns",
  l="label",
  p="perspective",
  t="transparency",
@@ -646,12 +645,12 @@ def plot(self, x=None, y=None, data=None, sizes=None, direction=None, **kwargs):
  If a symbol is selected and no symbol size given, then plot will
  interpret the third column of the input data as symbol size. Symbols
  whose size is <= 0 are skipped. If no symbols are specified then the
- symbol code (see **style** below) must be present as last column in the
- input. If **style** is not used, a line connecting the data points will
- be drawn instead. To explicitly close polygons, use **close**. Select a
- fill with **color**. If **color** is set, **pen** will control whether
- the polygon outline is drawn or not. If a symbol is selected, **color**
- and **pen** determines the fill and outline/no outline, respectively.
+ symbol code (see *style* below) must be present as last column in the
+ input. If *style* is not used, a line connecting the data points will
+ be drawn instead. To explicitly close polygons, use *close*. Select a
+ fill with *color*. If *color* is set, *pen* will control whether the
+ polygon outline is drawn or not. If a symbol is selected, *color* and
+ *pen* determines the fill and outline/no outline, respectively.
 
  Full option list at :gmt-docs:`plot.html`
 
@@ -676,10 +675,10 @@ def plot(self, x=None, y=None, data=None, sizes=None, direction=None, **kwargs):
  depending on the style options chosen.
  {J}
  {R}
- straight_lines : bool or str
+ straight_line : bool or str
  ``[m|p|x|y]``.
  By default, geographic line segments are drawn as great circle
- arcs. To draw them as straight lines, use *straight_lines*.
+ arcs. To draw them as straight lines, use *straight_line*.
  Alternatively, add **m** to draw the line by first following a
  meridian, then a parallel. Or append **p** to start following a
  parallel, then a meridian. (This can be practical to draw a line
@@ -694,7 +693,7 @@ def plot(self, x=None, y=None, data=None, sizes=None, direction=None, **kwargs):
  Offset the plot symbol or line locations by the given amounts
  *dx/dy* [Default is no offset]. If *dy* is not given it is set
  equal to *dx*.
- error_bars : bool or str
+ error_bar : bool or str
  ``[x|y|X|Y][+a][+cl|f][+n][+wcap][+ppen]``.
  Draw symmetrical error bars. Full documentation is at
  :gmt-docs:`plot.html#e`.